Introduction

SAGT chose the fossil Lepidodendron (the so-called Scale Tree) as its motif because
of its extensive occurrence in the local
Coal Measure rocks and because it represents a significant episode in the colonisation of land by
a remarkable group of plants.

Lepidodendron was a lycopod, not an angiosperm - like an oak tree nor a gymnosperm -
like a conifer tree. (See Fig 2). Those modern plants evolved much later than the lycopods and are
very familiar to us, but they have very little in common with these Carboniferous plants whose
internal structure, roots, reproductive system and even their leaves evolved in a different
way from modern trees. This means that when we describe the features of lycopods we should use
a different set of names for what look like familiar features.
See Lepidodendron Morphology

The first plants on Earth evolved in the oceans and then, much later, colonised the land. By about 470 million
years ago terrestrial green plants, like liverworts and mosses, probably only a few centimetres
tall, were producing the first spores in the fossil record. These were simple forms with basic adaptations
to land dwelling, but it was from these early forms that taller land plants evolved.

The adaptions required for any plant to evolve successfully from an aquatic, marine environment to
a terrestrial one are:

A waterproof surface cuticle

Stoma (breathing holes) and internal channels to allow gas exchange, but control water loss

A root system to obtain water and nutrients

A vascular (plumbing) system to conduct water to all parts of the plant

A reproductive system that worked in air, not seawater, and conserved water, especially the evolution
of spores with durable walls

An internal support system to allow the plant to become taller to compete for more sunlight

Early lycopods also existed in the Late Devonian, and these were smaller ancestors to the giant Carboniferous
lycopods that developed a remarkable and unique stigmarian rooting system enabling them to dominate the coal
swamp ecosystems when they became widespread during the Westphalian.
See Lycopod Palaeoecology